Pacemakers place one or more wires into heart muscle to trigger electro-mechanically coupled contraction. A single wire to the right atrium is called an AAI pacemaker (atrial sensing, atrial triggering, inhibit triggering if sensed). A single wire to the right ventricle is called a VVI pacemaker (ventricular sensing, ventricular triggering, inhibit if sensed). With two wires to the heart more combinations are possible, including atrial-ventricular sequential activation, a closer mimic to normal function (DDDR pacemaker: dual sensing, dual triggering, dual functions, and rate-responsive to mimic exercise adjustment of heart rate). Three wires are used for synchronization: one to the right atrium, one to the right ventricle apex, and a third lead into a distal branch of the coronary sinus to activate the far side of the left ventricle. Resynchronization is used to compensate for a dilated ventricle, especially one with conduction delays, where the timing of activation is so unbalanced that the heart contraction approaches a wobbling motion rather than a well coordinated contraction. Adjusting timing of activation of the right ventricle and left ventricle can offset dysynchrony (unbalanced timing) and thereby increase the amount of blood ejected by each heart beat contraction (ejection fraction). Patients with dilated cardiomyopathy and significant conduction delays can improve the ejection fraction by 10 or more percentage points, which offers a significant improvement in exertion tolerance and heart failure symptoms.

Patients with ejection fraction below 35%, among others, have an elevated risk of life-ending arrhythmias such as ventricular tachycardia. Ventricular tachycardia is an extreme example of a wobbling heart in which the electrical activation sequence circles around the heart sequentially activating a portion and blocking its ability to respond until the electric signal comes around again. Whenever a portion of the heart is activated, ions shift location, and further activation of that region is not possible until sufficient time passes so that the compartmentalized ion concentrations can be restored (repolarization). Pacing can interrupt ventricular tachycardia by depolarizing a region that supported the circular activation pattern. Failing that, an electric shock can stop an ineffective rhythm. After all regions stop activation, they will generally reactivate in the normal pulsatile synchronous manner. An implanted cardiac defibrillator is a device designed to apply an internal electric shock to pause all activation and thereby interrupt ventricular tachycardia.UPDATED on 12/31/2013

When we think of Pacemakers and ICD’s we naturally think of a ‘Can’ and Leads that track down into the heart. Whilst these devices work fantastically well and will continue to do so. Unfortunately the ‘lead’ part of the device opens the door for a few complications to possibly arise. Those who have a Pacemaker or ICD will probably be familiar with concerns over;

Systemic Infection – Infections travelling down the Leads into the Heart

Lead Displacement – The Lead moving away from the heart tissue and thus becoming pretty useless.

Vascular/Organ Injury – Damage to the blood vessels being used for access or perforation of heart wall.

Pneumothorax (damage to the lining around the Lung), Haemothorax (build up of blood in the chest cavity), and air embolism (air bubble trapped in a blood vessel).

These complications are one of the key motivations behind developing ‘leadless’ devices the first of which the St Jude Nanostim, a small VVI Pacemaker that fits directly into the heart.

Another device to address these issues is the Boston Scientific S-ICD

What is the Boston Scientific S-ICD?

The S-ICD is what is sometimes referred to as a ‘shock box’ it does not have the pacemaker functionality that many other ICD’s do have. It is ONLY there to terminate dangerous Arrhythmias.

*It does not have the pacing functionality of traditional ICD‘s because it DOES NOT HAVE A LEAD THAT ENTERS THE HEART.*

Without the lead(s) ENTERING the heart via a blood vessel there is a reduction in the risks mentioned previously that are associated traditional device. Another of the benefits is that the S-ICD is positioned and implanted using anatomical landmarks (visible parts of your body) and not Fluoroscopy (video X-Ray) which reduces radiation exposure to the patient.

Positioning of the S-ICD.

The ‘Can‘ (metal box that contains all the circuitry and battery), is buried under the skin on the outside of the ribs. Put your arms down by your sides, the device would go where your ribs meet the middle of your bicep. A lead is then run under the skin to the centre of your chest where its is anchored and then north, under the skin again until the tip of the lead is roughly at the top of the sternum.

For you physicians out there the ‘can’ is positioned at the mid-axillary line between the 5th and 6th intercostal spaces, the lead is then tunnelled to a small Xiphoid incision and then tunnelled north to a superior incision.

How is an S-ICD Implanted?

Having spoken to Boston Scientific it is becoming more apparent that the superior incision (cut at the top of the chest) may actually be removed from the procedure guidance as simply tunnelling the lead and ‘wedging’ the tip at that point is satisfactory – THIS IS NOT CONFIRMED AT THE MOMENT AND IS THEREFORE NOT PROCEDURE ADVICE.

How does the S-ICD Work?

A ‘Shock Box’ basically needs to do 2 things. Firstly be able to SENSE if the heart has entered a Dangerous Arrhythmia and Secondly, be able to treat it.

The treatment part of the functionality is the easy bit – it delivers an electric shock across a ‘circuit’ that involves a large amount of the tissue in the heart. The lead has two ‘electrodes’ and the ‘Can’ is a third electrode allowing you different shocking ‘vectors’. By vectors we mean directions and area through which the electricity travels during a shock. This gives us extra options when implanting a device as some vectors will work better than others for the treatment of dangerous arrhythmias.

Shocking Vectors?

This is a concept you are familiar with without even thinking about it… when you are watching ER or another TV program and they Defibrillate the patient using the metal paddles, where do they position them? One either side of the heart? Precisely!! this is creating a ‘vector’ across the heart to involve the cardiac tissue. The paddles would be a lot less effective if you put one on the knee and one on the foot!

Now because the ‘Vectors’ used by the S-ICD are over a larger area than those with a traditional device – more energy has to be delivered to have the same desired affect. The upshot of this is that a larger battery is required to deliver the 80J! Bigger Battery = Bigger Box. This image shows a demo device but this is the exact size compared to a One Pound Coin! Now yes it is big but because of the extra room where they place the device it is pretty discrete and hidden in even slender patients.

STAT ATTACK!

The S-ICD System delivers up to 5 shocks per episode at 80 J with up to 128 seconds of ECG storage per episode and storage of up to 45 episodes.

The heart rate that the S-ICD is told to deliver therapy is programable between 170 and 250 bpm. Quite cleverly the device is able to also deliver a small amount of ‘pacing’ after a shock, when the heart can often run slowly. This is external pacing and will be felt!! It can run for 30s.

The S-ICD uses its electrodes to produce an ECG similar to a surface ECG.

Now the Sensing functionality is the devices ability to determine what Rhythm the heart is in! Without a lead in the heart to give us really accurate information the device is using a large area of heart, ribs and muscle. This means there is more potential for ‘artefact’. Artefact is the electrical interference and confusion – that could potentially lead to a patient being shocked when they do not require it – or not being shocked when they do…

Boston Scientific have come up with a very clever software/algorithm called ‘Insight’. Insight uses 3 separate methods to determine the nature of a heart rhythm.

The statistics for treatment success and inappropriate shocks (an electrocuted patient that did not need to be) actually compare very similarly if not favourably compared to other devices on the market – these two studies are well worth a read if you have the time 🙂

Well essentially anyone who qualifies for a normal ‘shock box’ ICD but with one other requirement. The Insight Software requires that a person has certain characteristics on their ECG. This is essentially showing that they have tall enough and narrow enough complexes to allow the algorithm to perform effectively. A simple 12 lead ECG Laying and Standing will be obtained and then a ‘Stencil’ is passed over the Print out – If the complexes fit within the boundaries marked on the ‘stencil’ then you potentially qualify. If your ECG does not meet requirements then it will not be recommended for you to have the S-ICD.

Abstract

Background—The prevalence rates and influencing factors for deployment of primary prevention implantable cardioverter defibrillators (ICDs) among subjects who eventually experience sudden cardiac arrest in the general population have not been evaluated.

Methods and Results—Cases of adult sudden cardiac arrest with echocardiographic evaluation before the event were identified from the ongoing Oregon Sudden Unexpected Death Study (population approximately 1 million). Eligibility for primary ICD implantation was determined from medical records based on established guidelines. The frequency of prior primary ICD implantation in eligible subjects was evaluated, and ICD nonrecipients were characterized. Of 2093 cases (2003–2012), 448 had appropriate pre– sudden cardiac arrest left ventricular ejection fraction information available. Of these, 92 (20.5%) were eligible for primary ICD implantation, 304 (67.9%) were ineligible because of left ventricular ejection fraction >35%, and the remainder (52, 11.6%) had left ventricular ejection fraction ≤35% but were ineligible on the basis of clinical guideline criteria. Among eligible subjects, only 12 (13.0%; 95% confidence interval, 6.1%–19.9%) received a primary ICD. Compared with recipients, primary ICD nonrecipients were older (age at ejection fraction assessment, 67.1±13.6 versus 58.5±14.8 years, P=0.05), with 20% aged ≥80 years (versus 0% among recipients, P=0.11). Additionally, a subgroup (26%) had either a clinical history of dementia or were undergoing chronic dialysis.

Conclusions—Only one fifth of the sudden cardiac arrest cases in the community were eligible for a primary prevention ICD before the event, but among these, a small proportion (13%) were actually implanted.Although older age and comorbidity may explain nondeployment in a subgroup of these cases, other determinants such as socioeconomic factors, health insurance, patient preference, and clinical practice patterns warrant further detailed investigation.

Cardiac resynchronization therapy (CRT) is a multilead pacing device that can extend lives and improve the quality of life of selected patients who suffer from reduced performance of the heart due to adverse timing of contraction (wobbling motion from conduction delays that cause asynchrony or delayed activation of one portion of the left ventricle compared to others reducing net blood ejection).

The degree of benefit in CRT responders depends not only on the degree of asynchrony, but also on the delayed activity location in relation to the available locations for lead placement. CRT is an adjustment in the timing of muscle activiation to improve the concerted impact on blood ejection. Only patients likely to improve should be exposed to the risks and costs of CRT.

Previous CRT studies enrolled patients with QRS duration >120 or >130 ms for synchronizing biventricular pacing. Additional work confirmed the greatest benefit occurred in patients with QRS durations >150 ms and typical left bundle branch block (LBBB). Conflicting observational and small randomized trials were less clear for patients with shorter QRS durations—the majority of heart-failure patients. What’s more, most cardiologists have seen patients with “modest” QRS durations respond to CRT. In theory, wide QRS is only expected if the axis of significant delay projects onto the standard ECG views, whereas significant opportunity for benefit can be missed if the axis of significant delay is not wide in the standard views. CRT implanters have heard of patients with normal-duration QRS where echo shows marked dyssynchrony. This raised the question: Are there CHF patients with mechanical dyssynchrony (determined by echo) but no electrical delay (as measured by the ECG) benefit from CRT?Unfortunately, echo does not resolve the issue either. Thus there is the residual question of who should be evaluated by a true 3D syncrhony assessment by cardiac MRI.

Echocardiographic techniques held promise to identify mechanical dyssynchrony, but like the standard 12 lead ECG, they also utilize limited orientations of views of the heart and hence the directions in which delays can be detected. Cardiac MRI Research (not limited in view angle) by JDPearlman showed that the axis of maximal delay in patients with asynchrony is within 30 degrees of the ECG and echo views in a majority of patients with asynchrony, but it can be 70-110 degrees away from the views used by echocardiography and by ECG in 20% of cases. Hence some patients who may benefit can be missed by ECG or Echo criteria.

Methodology

Echo-CRT was an industry-sponsored (Biotronik) investigator-initiated prospective international randomized controlled trial. All patients had mechanical dyssynchrony by echo, QRS <130 ms, and an ICD indication. CRT-D devices were implanted in all patients. Blinded randomization to CRT-on (404 patients) vs CRT-off (405 patients) was performed after implantation. Programming in the CRT-off group was set to minimize RV pacing. The primary outcome was a composite of all-cause mortality or hospitalization.

Six key findings

1. Although entry criteria for the trial was a QRS duration <130 ms, the mean QRS duration of both groups was 105 ms.

2. The data safety monitoring board terminated the trial prematurely because of an increased death rate in the CRT group.

3. No differences were noted in the primary outcome.

4. More patients died in the CRT group (hazard ratio=1.8).

5. The higher death rate in the CRT group was driven by cardiovascular death.

6. More patients in the CRT group were hospitalized, due primarily to device-related issues.

These findings send clear and simple messages to all involved with treating patients with heart failure. My interpretation of Echo-CRT is as follows:

The signal of increased death was strong. A hazard ratio of 1.8 translates to an almost doubling of the risk of death. This finding is unlikely to be a statistical anomaly, as it was driven by CV death. The risks of CRT in nonresponders are well-known and include: increased RV pacing, possible proarrhythmia from LV pacing, and the need for more device-related surgery. Patients who do not respond to CRT get none of the benefits but all the potential harms—an unfavorable ratio indeed.

Echo is not useful for assessing dyssynchrony in patients with narrow QRS complexes.

Dr Samuel Asirvatham explains the concept of electropathy in a review article in the Journal of Cardiovascular Electrophysiology. He teaches us that the later the LV lateral wall is activated relative to the RV, the more the benefit of preexciting the lateral wall with an LV lead. That’s why the benefit from CRT in many cases increases with QRS duration, because—in a majority—a wide QRS means late activation of the lateral LV.

Simple triumphs over complicated—CRT response best estimated with the old-fashioned ECG.

In a right bundle branch block, the left ventricle is activated first; in LBBB, the LV lateral wall is last, and with a nonspecific ICD, there’s delayed conduction in either the His-Purkinje system or in ventricular muscle. What does a normal QRS say? It says the wave front of activation as projected onto the electric views obtained activates the LV and RV simultaneously. If those views capture the worst delay then they can eliminate the need for resynchrony.

CRT benefit with mild-moderate QRS prolongation still not settled

Dr Robert Myerburg (here and here) teaches us to make a distinction between trial entry criteria and the actual values of the cohort.

Consider how this applies to QRS duration: COMPANIONand CARE-HFare clinical trials that showed definitive CRT benefit. Entry required a QRS duration >120 ms (130 ms in CARE-HF). But the actual mean QRS duration of enrolled patients was 160 ms. A meta-analysis of CRT trials confirmed benefit at longer QRS durations and questioned it below 150 ms. CRT guideline recommendations incorporate study entry criteria, not the mean values of actual patients in the trial. Patients enrolled in Echo-CRT had very narrow QRS complexes (105 ms). What to recommend in the common situation when a patient with a typical LBBB has a QRS duration straddling 130 ms is not entirely clear. The results of Echo-CRT might have been different had the actual QRS duration values been closer to 130 ms.

Conclusion

Echo-CRT study reinforces expectations based on cardiac physiology. In the practice of medicine, it’s quite useful to know when not to do something.

The trial should not dampen enthusiasm for CRT. Rather, it should focus our attention to patient selection—and the value of the 12-lead ECG.

Medtronic Pacemaker Recall

Australia’s regulatory authority, the Therapeutic Goods Administration (TGA) has issued a hazard alert pertaining to one of Medtronic’s pacing devices, the Consulta® Cardiac Resynchronization Therapy Pacemaker (CRT-P). The alert coincides somewhat with Medtronic’s own issuance of a field safety notice concerning Consulta and Syncra® CRT-P devices.

Background

Consulta and Syncra CRT-Ps are implantable medical devices used to treat heart failure. The devices provide pacing to help coordinate the heart’s pumping action and improve blood flow.

The two devices are the subject of a global manufacturer recall after Medtronic had identified an issue with a subset of both during production, although as yet there had been no reported or confirmed device failures. However, because of the potential for malfunction, Medtronic is requiring the return of non-implanted devices manufactured between April 1 and May 13, 2013 for re-inspection.

Seemingly this manufacturing issue could compromise the sealing of the device. Should an out-of-spec weld fail this could result in body fluids entering the device, which could cause it to malfunction leading to loss of pacing output. This could potentially see the return of symptoms including

fainting or lightheadedness,

dyspnoea (shortness of breath),

fatigue and

oedema.

Medtronic’s recall is thought to relate to 265 devices, 44 of which have been implanted in the US.

The Australian warning letter, issued by the TGA states that only one “at risk” Consulta CRT-P device has been implanted in the country and there have been no reports of device failures or patient injuries relating to this issue.

Neither Medtronic nor the TGA are suggesting any specific patient management measures other than routine follow-up in accordance with labelling instructions.

Pacemaker/Implantable Cardioverter Defibrillator (ICD) Insertion

Procedure Overview

What is a pacemaker/implantable cardioverter defibrillator (ICD) insertion?

A pacemaker/implantable cardioverter defibrillator (ICD) insertion is a procedure in which a pacemaker and/or an ICD is inserted to assist in regulating problems with the heart rate (pacemaker) or heart rhythm (ICD).

Pacemaker

When a problem develops with the heart’s rhythm, such as a slow rhythm, a pacemaker may be selected for treatment. A pacemaker is a small electronic device composed of three parts: a generator, one or more leads, and an electrode on each lead. A pacemaker signals the heart to beat when the heartbeat is too slow.

Click Image to Enlarge

A generator is the “brain” of the pacemaker device. It is a small metal case that contains electronic circuitry and a battery. The lead (or leads) is an insulated wire that is connected to the generator on one end, with the other end placed inside one of the heart’s chambers.

The electrode on the end of the lead touches the heart wall. In most pacemakers, the lead senses the heart’s electrical activity. This information is relayed to the generator by the lead.

If the heart’s rate is slower than the programmed limit, an electrical impulse is sent through the lead to the electrode and the pacemaker’s electrical impulse causes the heart to beat at a faster rate.

When the heart is beating at a rate faster than the programmed limit, the pacemaker will monitor the heart rate, but will not pace. No electrical impulses will be sent to the heart unless the heart’s natural rate falls below the pacemaker’s low limit.

Pacemaker leads may be positioned in the atrium or ventricle or both, depending on the condition requiring the pacemaker to be inserted. An atrial dysrhythmia/arrhythmia (an abnormal heart rhythm caused by a dysfunction of the sinus node or the development of another atrial pacemaker within the heart tissue that takes over the function of the sinus node) may be treated with an atrial pacemaker.

Click Image to Enlarge

A ventricular dysrhythmia/arrhythmia (an abnormal heart rhythm caused by a dysfunction of the sinus node, an interruption in the conduction pathways, or the development of another pacemaker within the heart tissue that takes over the function of the sinus node) may be treated with a ventricular pacemaker whose lead wire is located in the ventricle.

It is possible to have both atrial and ventricular dysrhythmias, and there are pacemakers that have lead wires positioned in both the atrium and the ventricle. There may be one lead wire for each chamber, or one lead wire may be capable of sensing and pacing both chambers.

A new type of pacemaker, called a biventricular pacemaker, is currently used in the treatment of congestive heart failure. Sometimes in heart failure, the two ventricles (lower heart chambers) do not pump together in a normal manner. When this happens, less blood is pumped by the heart.

A biventricular pacemaker paces both ventricles at the same time, increasing the amount of blood pumped by the heart. This type of treatment is called cardiac resynchronization therapy.

Implantable cardioverter defibrillator (ICD)

An implantable cardioverter defibrillator (ICD) looks very similar to a pacemaker, except that it is slightly larger. It has a generator, one or more leads, and an electrode for each lead. These components work very much like a pacemaker. However, the ICD is designed to deliver an electrical shock to the heart when the heart rate becomes dangerously fast, or €œfibrillates.”

An ICD senses when the heart is beating too fast and delivers an electrical shock to convert the fast rhythm to a normal rhythm. Some devices combine a pacemaker and ICD in one unit for persons who need both functions.

The ICD has another type of treatment for certain fast rhythms called anti-tachycardia pacing (ATP). When ATP is used, a fast pacing impulse is sent to correct the rhythm. After the shock is delivered, a “back-up” pacing mode is used if needed for a short while.

The procedure for inserting a pacemaker or an ICD is the same. The procedure generally is performed in an electrophysiology (EP) lab or a cardiac catheterization lab.

The heart’s electrical conduction system

Click Image to Enlarge

The heart is, in the simplest terms, a pump made up of muscle tissue. Like all pumps, the heart requires a source of energy in order to function. The heart’s pumping energy comes from an indwelling electrical conduction system.

An electrical stimulus is generated by the sinus node (also called the sinoatrial node, or SA node), which is a small mass of specialized tissue located in the right atrium (right upper chamber) of the heart.

The sinus node generates an electrical stimulus regularly at 60 to 100 times per minute under normal conditions. This electrical stimulus travels down through the conduction pathways (similar to the way electricity flows through power lines from the power plant to your house) and causes the heart’s chambers to contract and pump out blood.

The right and left atria (the two upper chambers of the heart) are stimulated first and contract a short period of time before the right and left ventricles (the two lower chambers of the heart).

The electrical impulse travels from the sinus node to the atrioventricular (AV) node, where it stops for a very short period, then continues down the conduction pathways via the “bundle of His” into the ventricles. The bundle of His divides into right and left pathways to provide electrical stimulation to both ventricles.

What is an ECG?

This electrical activity of the heart is measured by an electrocardiogram (ECG or EKG). By placing electrodes at specific locations on the body (chest, arms, and legs), a tracing of the electrical activity can be obtained. Changes in an ECG from the normal tracing can indicate one or more of several heart-related conditions.

Dysrhythmias/arrhythmias (abnormal heart rhythms) are diagnosed by methods such as EKG, Holter monitoring, signal-average EKG, or electrophysiological studies. These symptoms may be treated with medication or procedures such as a cardiac ablation (removal of a location in the heart that is causing a dysrhythmia by freezing or radiofrequency).

Reasons for the Procedure

A pacemaker may be inserted in order to provide stimulation for a faster heart rate when the heart is beating too slowly, and when other treatment methods, such as medication, have not improved the heart rate.

An ICD may be inserted in order to provide fast pacing (ATP), cardioversion (small shock), or defibrillation (larger shock) when the heart beats too fast.

Problems with the heart rhythm may cause difficulties because the heart is unable to pump an adequate amount of blood to the body. If the heart rate is too slow, the blood is pumped too slowly.

If the heart rate is too fast or too irregular, the heart chambers are unable to fill up with enough blood to pump out with each beat. When the body does not receive enough blood, symptoms such as fatigue, dizziness, fainting, and/or chest pain may occur.

Some examples of rhythm problems for which a pacemaker or ICD might be inserted include:

heart block – occurs when the electrical signal is delayed after leaving the SA node; there are several types of heart blocks, and each one has a distinctive ECG tracing

There may be other reasons for your physician to recommend a pacemaker or ICD insertion.

Risks of the Procedure

Possible risks of pacemaker or ICD insertion include, but are not limited to, the following:

bleeding from the incision or catheter insertion site

damage to the vessel at the catheter insertion site

infection of the incision or catheter site

pneumothorax – air becomes trapped in the pleural space causing the lung to collapse

If you are pregnant or suspect that you may be pregnant, you should notify your physician. If you are lactating, or breastfeeding, you should notify your physician.

Patients who are allergic to or sensitive to medications or latex should notify their physician.

For some patients, having to lie still on the procedure table for the length of the procedure may cause some discomfort or pain.

There may be other risks depending upon your specific medical condition. Be sure to discuss any concerns with your physician prior to the procedure.

Before the Procedure

Your physician will explain the procedure to you and offer you the opportunity to ask any questions that you might have about the procedure.

You will be asked to sign a consent form that gives your permission to do the test. Read the form carefully and ask questions if something is not clear.

You will need to fast for a certain period of time prior to the procedure. Your physician will notify you how long to fast, usually overnight.

If you are pregnant or suspect that you are pregnant, you should notify your physician.

Notify your physician if you are sensitive to or are allergic to any medications, iodine, latex, tape, or anesthetic agents (local and general).

Notify your physician of all medications (prescription and over-the-counter) and herbal supplements that you are taking.

Notify your physician if you have heart valve disease, as you may need to receive an antibiotic prior to the procedure.

Notify your physician if you have a history of bleeding disorders or if you are taking any anticoagulant (blood-thinning) medications, aspirin, or other medications that affect blood clotting. It may be necessary for you to stop some of these medications prior to the procedure.

Your physician may request a blood test prior to the procedure to determine how long it takes your blood to clot. Other blood tests may be done as well.

You may receive a sedative prior to the procedure to help you relax. If a sedative is given, you will need someone to drive you home afterwards.

The upper chest may be shaved or clipped prior to the procedure.

Based upon your medical condition, your physician may request other specific preparation.

During the Procedure

Chest X-ray with Implanted Pacemaker

A pacemaker or implanted cardioverter defibrillator may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your physician’s practices.

Generally, a pacemaker or ICD insertion follows this process:

You will be asked to remove any jewelry or other objects that may interfere with the procedure.

You will be asked to remove your clothing and will be given a gown to wear.

You will be asked to empty your bladder prior to the procedure.

An intravenous (IV) line will be started in your hand or arm prior to the procedure for injection of medication and to administer IV fluids, if needed.

You will be placed in a supine (on your back) position on the procedure table.

You will be connected to an electrocardiogram (ECG or EKG) monitor that records the electrical activity of the heart and monitors the heart during the procedure using small, adhesive electrodes. Your vital signs (heart rate, blood pressure, breathing rate, and oxygenation level) will be monitored during the procedure.

Large electrode pads will be placed on the front and back of the chest.

You will receive a sedative medication in your IV before the procedure to help you relax. However, you will likely remain awake during the procedure.

The pacemaker or ICD insertion site will be cleansed with antiseptic soap.

Sterile towels and a sheet will be placed around this area.

A local anesthetic will be injected into the skin at the insertion site.

Once the anesthetic has taken effect, the physician will make a small incision at the insertion site.

A sheath, or introducer, is inserted into a blood vessel, usually under the collarbone. The sheath is a plastic tube through which the pacer/ICD lead wire will be inserted into the blood vessel and advanced into the heart.

It will be very important for you to remain still during the procedure so that the catheter placement will not be disturbed and to prevent damage to the insertion site.

The lead wire will be inserted through the introducer into the blood vessel. The physician will advance the lead wire through the blood vessel into the heart.

Once the lead wire is inside the heart, it will be tested to verify proper location and that it works. There may be one, two, or three lead wires inserted, depending on the type of device your physician has chosen for your condition. Fluoroscopy, (a special type of x-ray that will be displayed on a TV monitor), may be used to assist in testing the location of the leads.

Once the lead wire has been tested, an incision will be made close to the location of the catheter insertion (just under the collarbone). You will receive local anesthetic medication before the incision is made.

The pacemaker/ICD generator will be slipped under the skin through the incision after the lead wire is attached to the generator. Generally, the generator will be placed on the non-dominant side. (If you are right-handed, the device will be placed in your upper left chest. If you are left-handed, the device will be placed in your upper right chest).

The ECG will be observed to ensure that the pacer is working correctly.

The skin incision will be closed with sutures, adhesive strips, or a special glue.

A sterile bandage/dressing will be applied.

After the Procedure

In the hospital

After the procedure, you may be taken to the recovery room for observation or returned to your hospital room. A nurse will monitor your vital signs for a specified period of time.

You should immediately inform your nurse if you feel any chest pain or tightness, or any other pain at the incision site.

After the specified period of bed rest has been completed, you may get out of bed. The nurse will assist you the first time you get up, and will check your blood pressure while you are lying in bed, sitting, and standing. You should move slowly when getting up from the bed to avoid any dizziness from the period of bedrest.

You will be able to eat or drink once you are completely awake.

The insertion site may be sore or painful, but pain medication may be administered if needed.

Your physician will visit with you in your room while you are recovering. The physician will give you specific instructions and answer any questions you may have.

Once your blood pressure, pulse, and breathing are stable and you are alert, you will be taken to your hospital room or discharged home.

If the procedure is performed on an outpatient basis, you may be allowed to leave after you have completed the recovery process. However, if there are concerns or problems with your ECG, you may stay in the hospital for an additional day (or longer) for monitoring of the ECG.

You should arrange to have someone drive you home from the hospital following your procedure.

At home

You should be able to return to your daily routine within a few days. Your physician will tell you if you will need to take more time in returning to your normal activities. In addition, you should not do any lifting or pulling on anything for a few weeks. You may be instructed not to lift your arms above your head for a period of time.

You will most likely be able to resume your usual diet, unless your physician instructs you differently.

It will be important to keep the insertion site clean and dry. Your physician will give you specific bathing instructions.

Your physician will give you specific instructions about driving. If you had an ICD, you will not be able to drive until your physician gives you approval. Your physician will explain these limitations to you, if they are applicable to your situation.

You will be given specific instructions about what to do if your ICD discharges a shock. For example, you may be instructed to dial 911 or go to the nearest emergency room in the event of a shock from the ICD.

Ask your physician when you will be able to return to work. The nature of your occupation, your overall health status, and your progress will determine how soon you may return to work.

Notify your physician to report any of the following:

fever and/or chills

increased pain, redness, swelling, or bleeding or other drainage from the insertion site

Your physician may give you additional or alternate instructions after the procedure, depending on your particular situation.

Pacemaker/ICD precautions

The following precautions should always be considered. Discuss the following in detail with your physician, or call the company that made your device:

Always carry an ID card that states you are wearing a pacemaker or an ICD. In addition, you should wear a medical identification bracelet that states you have a pacemaker or ICD.

Use caution when going through airport security detectors. Check with your physician about the safety of going through such detectors with your type of pacemaker. In particular, you may need to avoid being screened by hand-held detector devices, as these devices may affect your pacemaker.

You may not have a magnetic resonance imaging (MRI) procedure. You should also avoid large magnetic fields.

Abstain from diathermy (the use of heat in physical therapy to treat muscles).

Turn off large motors, such as cars or boats, when working on them (they may temporarily €œconfuse” your device).

Avoid certain high-voltage or radar machinery, such as radio or television transmitters, electric arc welders, high-tension wires, radar installations, or smelting furnaces.

If you are having a surgical procedure performed by a surgeon or dentist, tell your surgeon or dentist that you have a pacemaker or ICD, so that electrocautery will not be used to control bleeding (the electrocautery device can change the pacemaker settings).

You may have to take antibiotic medication before any medically invasive procedure to prevent infections that may affect the pacemaker.

Always consult your physician if you have any questions concerning the use of certain equipment near your pacemaker.

When involved in a physical, recreational, or sporting activity, you should avoid receiving a blow to the skin over the pacemaker or ICD. A blow to the chest near the pacemaker or ICD can affect its functioning. If you do receive a blow to that area, see your physician.

Always consult your physician when you feel ill after an activity, or when you have questions about beginning a new activity.

In Summary: Who Needs a Pacemaker?

Doctors recommend pacemakers for many reasons. The most common reasons are bradycardia and heart block.

Bradycardia is a heartbeat that is slower than normal. Heart block is a disorder that occurs if an electrical signal is slowed or disrupted as it moves through the heart.

Heart block can happen as a result of aging, damage to the heart from a heart attack, or other conditions that disrupt the heart’s electrical activity. Some nerve and muscle disorders also can cause heart block, including muscular dystrophy.

Your doctor also may recommend a pacemaker if:

Aging or heart disease damages your sinus node’s ability to set the correct pace for your heartbeat. Such damage can cause slower than normal heartbeats or long pauses between heartbeats. The damage also can cause your heart to switch between slow and fast rhythms. This condition is called sick sinus syndrome.

You’ve had a medical procedure to treat an arrhythmia called atrial fibrillation. A pacemaker can help regulate your heartbeat after the procedure.

You need to take certain heart medicines, such as beta blockers. These medicines can slow your heartbeat too much.

You faint or have other symptoms of a slow heartbeat. For example, this may happen if the main artery in your neck that supplies your brain with blood is sensitive to pressure. Just quickly turning your neck can cause your heart to beat slower than normal. As a result, your brain might not get enough blood flow, causing you to feel faint or collapse.

Before recommending a pacemaker, your doctor will consider any arrhythmia symptoms you have, such as dizziness, unexplained fainting, or shortness of breath. He or she also will consider whether you have a history of heart disease, what medicines you’re currently taking, and the results of heart tests.

Diagnostic Tests

Many tests are used to detect arrhythmias. You may have one or more of the following tests.

EKG (Electrocardiogram)

An EKG is a simple, painless test that detects and records the heart’s electrical activity. The test shows how fast your heart is beating and its rhythm (steady or irregular).

An EKG also records the strength and timing of electrical signals as they pass through your heart. The test can help diagnose bradycardia and heart block (the most common reasons for needing a pacemaker).

A standard EKG only records the heartbeat for a few seconds. It won’t detect arrhythmias that don’t happen during the test.

To diagnose heart rhythm problems that come and go, your doctor may have you wear a portable EKG monitor. The two most common types of portable EKGs are Holter and event monitors.

Holter and Event Monitors

A Holter monitor records the heart’s electrical activity for a full 24- or 48-hour period. You wear one while you do your normal daily activities. This allows the monitor to record your heart for a longer time than a standard EKG.

An event monitor is similar to a Holter monitor. You wear an event monitor while doing your normal activities. However, an event monitor only records your heart’s electrical activity at certain times while you’re wearing it.

For many event monitors, you push a button to start the monitor when you feel symptoms. Other event monitors start automatically when they sense abnormal heart rhythms.

You can wear an event monitor for weeks or until symptoms occur.

Echocardiography

Echocardiography (echo) uses sound waves to create a moving picture of your heart. The test shows the size and shape of your heart and how well your heart chambers and valves are working.

Echo also can show areas of poor blood flow to the heart, areas of heart muscle that aren’t contracting normally, and injury to the heart muscle caused by poor blood flow.

Electrophysiology Study

For this test, a thin, flexible wire is passed through a vein in your groin (upper thigh) or arm to your heart. The wire records the heart’s electrical signals.

Your doctor uses the wire to electrically stimulate your heart. This allows him or her to see how your heart’s electrical system responds. This test helps pinpoint where the heart’s electrical system is damaged.

Stress Test

Some heart problems are easier to diagnose when your heart is working hard and beating fast.

During stress testing, you exercise to make your heart work hard and beat fast while heart tests, such as an EKG or echo, are done. If you can’t exercise, you may be given medicine to raise your heart rate.

What Are the Risks of Pacemaker Surgery?

Pacemaker surgery generally is safe. If problems do occur, they may include:

Swelling, bleeding, bruising, or infection in the area where the pacemaker was placed

Blood vessel or nerve damage

A collapsed lung

A bad reaction to the medicine used during the procedure

Talk with your doctor about the benefits and risks of pacemaker surgery.

How Does a Pacemaker Work?

A pacemaker consists of a battery, a computerized generator, and wires with sensors at their tips. (The sensors are called electrodes.) The battery powers the generator, and both are surrounded by a thin metal box. The wires connect the generator to the heart.

A pacemaker helps monitor and control your heartbeat. The electrodes detect your heart’s electrical activity and send data through the wires to the computer in the generator.

If your heart rhythm is abnormal, the computer will direct the generator to send electrical pulses to your heart. The pulses travel through the wires to reach your heart.

Newer pacemakers can monitor your blood temperature, breathing, and other factors. They also can adjust your heart rate to changes in your activity.

The pacemaker’s computer also records your heart’s electrical activity and heart rhythm. Your doctor will use these recordings to adjust your pacemaker so it works better for you.

Your doctor can program the pacemaker’s computer with an external device. He or she doesn’t have to use needles or have direct contact with the pacemaker.

Pacemakers have one to three wires that are each placed in different chambers of the heart.

The wires in a single-chamber pacemaker usually carry pulses from the generator to the right ventricle (the lower right chamber of your heart).

The wires in a dual-chamber pacemaker carry pulses from the generator to the right atrium (the upper right chamber of your heart) and the right ventricle. The pulses help coordinate the timing of these two chambers’ contractions.

The wires in a biventricular pacemaker carry pulses from the generator to an atrium and both ventricles. The pulses help coordinate electrical signaling between the two ventricles. This type of pacemaker also is called a cardiac resynchronization therapy (CRT) device.

Cross-Section of a Chest With a Pacemaker

The image shows a cross-section of a chest with a pacemaker. Figure A shows the location and general size of a double-lead, or dual-chamber, pacemaker in the upper chest. The wires with electrodes are inserted into the heart’s right atrium and ventricle through a vein in the upper chest. Figure B shows an electrode electrically stimulating the heart muscle. Figure C shows the location and general size of a single-lead, or single-chamber, pacemaker in the upper chest.

Types of Pacemaker Programming

The two main types of programming for pacemakers are

demand pacing and

rate-responsive pacing.

A demand pacemaker monitors your heart rhythm. It only sends electrical pulses to your heart if your heart is beating too slow or if it misses a beat.

A rate-responsive pacemaker will speed up or slow down your heart rate depending on how active you are. To do this, the device monitors your

sinus node rate,

breathing,

blood temperature, and

other factors to determine your activity level.

Your doctor will work with you to decide which type of pacemaker is best for you.

What To Expect During Pacemaker Surgery

Placing a pacemaker requires minor surgery. The surgery usually is done in a hospital or special heart treatment laboratory.

Before the surgery, an intravenous (IV) line will be inserted into one of your veins. You will receive medicine through the IV line to help you relax. The medicine also might make you sleepy.

Your doctor will numb the area where he or she will put the pacemaker so you don’t feel any pain. Your doctor also may give you antibiotics to prevent infection.

First, your doctor will insert a needle into a large vein, usually near the shoulder opposite your dominant hand. Your doctor will then use the needle to thread the pacemaker wires into the vein and to correctly place them in your heart.

An x-ray “movie” of the wires as they pass through your vein and into your heart will help your doctor place them. Once the wires are in place, your doctor will make a small cut into the skin of your chest or abdomen.

He or she will slip the pacemaker’s small metal box through the cut, place it just under your skin, and connect it to the wires that lead to your heart. The box contains the pacemaker’s battery and generator.

Once the pacemaker is in place, your doctor will test it to make sure it works properly. He or she will then sew up the cut. The entire surgery takes a few hours.

What To Expect After Pacemaker Surgery

Expect to stay in the hospital overnight so your health care team can check your heartbeat and make sure your pacemaker is working well. You’ll likely have to arrange for a ride to and from the hospital because your doctor may not want you to drive yourself.

For a few days to weeks after surgery, you may have pain, swelling, or tenderness in the area where your pacemaker was placed. The pain usually is mild; over-the-counter medicines often can relieve it. Talk to your doctor before taking any pain medicines.

Your doctor may ask you to avoid vigorous activities and heavy lifting for about a month after pacemaker surgery. Most people return to their normal activities within a few days of having the surgery.

How Will a Pacemaker Affect My Lifestyle?

Once you have a pacemaker, you have to avoid close or prolonged contact with electrical devices or devices that have strong magnetic fields. Devices that can interfere with a pacemaker include:

Cell phones and MP3 players (for example, iPods)

Household appliances, such as microwave ovens

High-tension wires

Metal detectors

Industrial welders

Electrical generators

These devices can disrupt the electrical signaling of your pacemaker and stop it from working properly. You may not be able to tell whether your pacemaker has been affected.

How likely a device is to disrupt your pacemaker depends on how long you’re exposed to it and how close it is to your pacemaker.

To be safe, some experts recommend not putting your cell phone or MP3 player in a shirt pocket over your pacemaker (if the devices are turned on).

You may want to hold your cell phone up to the ear that’s opposite the site where your pacemaker is implanted. If you strap your MP3 player to your arm while listening to it, put it on the arm that’s farther from your pacemaker.

You can still use household appliances, but avoid close and prolonged exposure, as it may interfere with your pacemaker.

You can walk through security system metal detectors at your normal pace. Security staff can check you with a metal detector wand as long as it isn’t held for too long over your pacemaker site. You should avoid sitting or standing close to a security system metal detector. Notify security staff if you have a pacemaker.

Some medical procedures can disrupt your pacemaker. These procedures include:

Magnetic resonance imaging, or MRI

Shock-wave lithotripsy to get rid of kidney stones

Electrocauterization to stop bleeding during surgery

Let all of your doctors, dentists, and medical technicians know that you have a pacemaker. Your doctor can give you a card that states what kind of pacemaker you have. Carry this card in your wallet. You may want to wear a medical ID bracelet or necklace that states that you have a pacemaker.

Physical Activity

In most cases, having a pacemaker won’t limit you from doing sports and exercise, including strenuous activities.

You may need to avoid full-contact sports, such as football. Such contact could damage your pacemaker or shake loose the wires in your heart. Ask your doctor how much and what kinds of physical activity are safe for you.

Ongoing Care

Your doctor will want to check your pacemaker regularly (about every 3 months). Over time, a pacemaker can stop working properly because:

Its wires get dislodged or broken

Its battery gets weak or fails

Your heart disease progresses

Other devices have disrupted its electrical signaling

To check your pacemaker, your doctor may ask you to come in for an office visit several times a year. Some pacemaker functions can be checked remotely using a phone or the Internet.

Your doctor also may ask you to have an EKG (electrocardiogram) to check for changes in your heart’s electrical activity.

Battery Replacement

Pacemaker batteries last between 5 and 15 years (average 6 to 7 years), depending on how active the pacemaker is. Your doctor will replace the generator along with the battery before the battery starts to run down.

Replacing the generator and battery is less-involved surgery than the original surgery to implant the pacemaker. Your pacemaker wires also may need to be replaced eventually.

Your doctor can tell you whether your pacemaker or its wires need to be replaced when you see him or her for followup visits.